Sources

About this site

This site explores the Pythagorean tetractys in geometry, number theory, harmonics, mysticism and philosophy. Its motto is: Number theory + geometry = philosophy.

Basis

The ideas, theses and structure go back to the German website tetraktys.de by Holger Ullmann, which was online from 2010 to 2016 and can still be viewed in the Internet Archive. The texts here are newly written. The graphics were recomputed from the underlying mathematics and made interactive wherever that made sense.

Images

All historical illustrations are in the public domain and come from Wikimedia Commons. The origin and licence of each image are listed under Image credits. All other graphics, from the triangles of points to the simplexes and the 3D models, are original constructions.

Literature

The most important books and further websites are collected under Links and media.

Technology

The site is built with Astro. The 3D models use three.js, all other graphics are SVG or canvas and are computed in the browser. The tones in the lambdoma and on the monochord are generated by the browser itself.